For the latest versions of git
Git merge --abort # this will allow you to undo merge conflicts.
This attempts to reset your working copy to whatever state it was in before the merge. That means that it should restore any uncommitted changes from before the merge, Generally, you shouldn't merge with uncommitted changes anyway.
For prior versions we use
git reset --merge
This is equivalent to the present syntax
Before version 1.6.2:
git reset --hard
which removes all uncommitted changes, including the uncommitted merge.
Hope this information will help you to resolve your query.